The present invention relates to a helicopter rotor head. More specifically, the invention relates to a helicopter rotor head which is free of flapping hinges as well as free of drag or lagging hinges. The rotor blades are supported by a flexible clamping or securing device.
Prior art hingeless rotors require at least two bearings for each blade or wing at the rotor head for taking up the forces and bending moments. Such prior art bearings have a compact structure which has a certain vulnerability, especially if used in military purpose helicopters.
Besides, the operating condition of these bearings cannot be easily ascertained without disassembling the bearing so that they require a periodically recurring maintenance effort.
Furthermore, where the rotor blades and the rotor head are made of fiber reinforced compound materials, it is necessary that the forces to be taken up by the bearing are introduced into the bearing by special hardware connected to the rotor blade, as well as to the rotor head. This type of structure therefore results in a higher manufacturing expense, as well as in additional structural weight. The structure disclosed in U.S. Pat. No. 3,880,551 suggests for avoiding the disadvantages of blade connections using conventional bearings and hardware, to interconnect two oppositely arranged rotor blades or wings by means of a carrier band which is clamped between transversely extending flexible cross bars. The carrier band, as well as the cross bars, are made of flexible glass fiber reinforced synthetic material. However, this type of structure is apparently not suitable for taking up the forces and moments which occur at the main rotor head of a helicopter because this known structure is intended for use, especially in connection with tail rotors in a helicopter.